Sit-ups, Curl-ups and Crunches Make Your Back Worse

And Twisting Sit-Ups Don’t Train Your Obliques, Either

There are hun­dreds of dif­fer­ent mus­cle groups in the human body. It’s com­pli­cat­ed to try to fig­ure out the exact role each mus­cle has. But every mus­cle works on the same basic prin­ci­ple:

When a mus­cle con­tracts, it exerts a force that short­ens the dis­tance between its two ends.

One of the major mus­cles of the abdomen – the rec­tus abdo­min­is – con­nects the front of your rib cage to the pelvis. When the rec­tus abdo­min­is con­tracts, it pulls the ribcage down towards your pelvis and bends your tor­so for­ward.

To high­light the action of the rec­tus abdo­min­is, place one hand on your low­er ribs and the oth­er on your low­er pelvis. Then bend your trunk so your two hands move clos­er to each oth­er. That’s what hap­pens when the rec­tus abdo­min­is con­tracts. In the med­ical uni­verse they call it trunk flex­ion.

When you do crunch­es, sit-ups, or curl-ups, you’re train­ing the rec­tus abdo­min­is to do its job of flex­ing the trunk.

But I’ve seen the down­side in many of my patients — with sit-ups, curl-ups, or crunch­es you’re actu­al­ly com­press­ing your spine and putting more pres­sure on your discs. That’s why most peo­ple should steer clear of these exer­cis­es.

For­tu­nate­ly, there are oth­er mus­cles of the abdomen that lie below the rec­tus abdo­min­is – the exter­nal and inter­nal obliques and thetrans­ver­sus abdo­min­is.

These deep­er-lying mus­cles have a dif­fer­ent archi­tec­ture and a dif­fer­ent func­tion. One end is attached to the side of your low­er ribs. And the oth­er end con­nects to a stiff sheet of con­nec­tive tis­sues in the front of your abdomen.

exter­nal obliques

When the oblique and trans­verse abdom­i­nals con­tract, they also pull their two ends towards each oth­er. But that doesn’t cause your trunk to flex. Instead, con­tract­ing these deep­er mus­cles sucks your abdom­i­nal wall back toward your spine.

To pic­ture the action, place one hand on the front of the abdomen and the oth­er on the sides of your low­er ribs. Now suck in your stom­ach to move your two hands clos­er to each oth­er. There’s lit­tle actu­al trunk move­ment. That illus­trates the action of the oblique and trans­verse mus­cles.

When the deep­er abdom­i­nals fire, they improve your pos­ture, make move­ment more effi­cient, and pro­tect your low back. That’s why they’re the most impor­tant mus­cles to train.

The plank pose is a sim­ple and effec­tive way to train these mus­cles.

Deepen Your Body of Knowledge

About Ronald Lavine, D.C.

Dr. Lavine has more than thirty five years' experience helping patients alleviate pain and restore health using diverse, scientifically-based manual therapy and therapeutic exercise and alignment methods.
His website, askdrlavine.com, provides more information about his approach.
Please contact him at drlavine@yourbodyofknowledge.com or at 212-400-9663.